What is wrong next to my oscar?

i bought an oscar about 3 weeks ago and he has been great. he have been very active and swims everywhere. but right in a minute he looks extremely pale and tends to stay near the heating system. the temp is about 79F.and he is properly fed. what could be wrong with him?
How long does it bear little snails...
You should get your dampen tested.
Why are our aquarium plants dying?
you don't state the size of the tank, several things spring to mind, you may have a fully clad filter however, the exchange rate of gasses may not be adequate.
The most likely cause though is that the Ph have dropped I would suggest you should test this, then do a partial dampen change and retest, also test the tap hose in a cup and leave it for 24hrs and retest this way you own 4 measurements, this should lead you to know the true level of your tap wet and whether the water is buffered and it breaks down. If the tap water is not to blame consequently I would suggest that your over feeding the fish and the detrious is breaking down in the gravel and cause the water to deteriorate to quickly and causing the crash.
You could lower the warmth to 76f and make the outlet of your filter hit the surface again if your over feeding you can sometimes bring back a film across the top causing gas exchange to become inefficient.
Where or who can i impart my...
Answers:    By properly feed, you mean you are giving him live food, as well as, cichlid pellets or flakes? If this is so, try getting your wet tested-take a small amount from the middle of your tank to any local pet store. It is also a good idea to buy the tryout strips & test it periodically yourself-to get familiar beside how the chemicals should be.
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